To easy diffs and avoid security issues.

Fixes bug #28590. Bugfix v0.4.0.

instead of bandwidth.
Forgotten when bandwidth was renamed to consensus_bandwidth in
9e089b72.

User torrc options in `extra_lines` that are only one key and not
a key value pair were not being parsed correctly.
Add a test.

Fixes bug #28715. Bugfix v0.1.1

when parsing user configuration, instead of modifying the one
passed to the function.

Fixes bug #28738. Bugfix v0.1.1

launch_tor is also parsing three sources of torrc options.
Move the `extra_lines` torrc option set by a user configuration
file to a function so that it can be tested.
Add docstring and remove comments.
Add sucess test.

Fixes bug #28738. Bugfix v0.1.1

Closes bug #28761. Bugfix v0.6.0

Fixes bug #28724. Bugfix v0.7.0.

since deb.torproject.org does not support anymore Trusty.

so that CI doesn't fail because of timeout trying to retrieve the
key.

Closes #28922. Bugfix v1.0.3-dev0

Since the data for the tests and the torflow scaling method was
changed in #bug28598, ajust the values after merging #28602.

Torflow's scaling now round digits according to Proposal 276,
but for compatibility with Torflow's round digits algorithm,
the argument option has to be available and by default be
Proposal 276.

The torflow-round-digs cli argument was kept, but it was added
other argument, round-digs, for the same option.
argparse takes the first argument as the variable name, but the
methods where still using torflow_round_digs.

Closes bug #28602. Bugfix 1.0.3-dev0.

When the descriptor or network status of a relay was not obtained,
some attributes can't be obtained it can be return None instead
of failing the measurement.
Also, there's no need for hasattr when getattr can just return
None as default.

Closes #28870. Bugfix v0.4.0

Destinations' Web servers must support TLS to avoid contents cache.

Fixes bug #28789. Bugfix v0.2.0.

Add a tox environment to check the links and call it from travis.
It's not run by tox in order to do not need Internet running tox.
The environment clean is also call from travis, in order to have
sphinx installed when checking the links.

Closes #28670.

Closes bug #28736. Bugfix v0.3.0.

The error that is returned by an exception, not a custom error.
So that it's easier to debug what fails.

bandwidth or rtt, so that it can be used to be stored and logged.

since it takes some seconds.

since it takes some seconds and the operator would not see any
progress at the beginning, until relays start to be measured.

When a new loop starts and when it ends, with the number of relays
measured and the time it took.

Warnings can make think the operator that sbws is not working,
while it's normal that some measurements fail.
Resultdump already logs at info level what succcess and what fails.
Keep these logs at debug level.